1. Field of the Invention
The present invention relates generally to artificial firelogs and particularly to artificial firelogs containing additives for improving the burn characteristics of the logs.
2. Description of the Related Art
Fireplaces have been used in homes over the years for providing heat as well as to provide a desired ambience. While wood and coal have been the primary fuels for burning in fireplaces, there is an increasing demand for manufactured or artificial fireplace logs. These logs are easier to purchase and store, provide better Btu/lb value than wood or coal, are easier to light, safer to use with virtually no maintenance during burning, and can be used to build fires of a known duration, generally from 2 hours to more than 6 hours.
Artificial firelogs are typically manufactured by combining a carrier material, usually particles of cellulosic origin, with a combustible binder/fuel. The cellulosic material may be sawdust, or a mixture of sawdust with other combustible materials of varying proportion. The binder typically consists of a suitable blend of waxes, either alone or in combination with other combustible materials. Additives imparting desired combustion characteristics, appearance, and other attributes may be combined with the basic ingredients. Following thorough mixing of the ingredients, the resulting mixture is formed into suitable, log-like shapes by extrusion, molding or compression, in either a batch or continuous process.
U.S. Pat. Nos. 3,297,419; 6,017,373; 6,136,054; 5,868,804; 4,333,738; 4,326,854; 3,843,336; and 4,040,796, incorporated herein by reference in their entireties, provide examples of known artificial firelog compositions, configurations and methods of manufacture.
While existing artificial firelog compositions can perform substantially as expected, there continues to be a need for further improvements in the burn characteristics of such compositions. For example, although a number of studies have shown that artificial (wax-sawdust) firelogs provide a substantial reduction in particulate matter (PM) and carbon monoxide (CO) emissions as compared with natural cordwood logs, there is a need to provide artificial firelogs that are still more environmentally-responsible, that is, firelogs which produce even lower levels of PM and CO both of which are classified by the Environmental Protection Agency as federal criteria pollutants.
The majority, by far, of PM emissions from the combustion of artificial firelogs (true as well for natural logs) are smaller than 2.5 microns in diameter, that is, they are classified as PM2.5 particles regarded as the most problematic from an air pollution standpoint.
CO is an odorless, highly toxic gas and residential indoor CO levels are of particular concern because of a trend toward the construction of airtight, energy-efficient residences. The National Ambient Air Quality Standard (NAAQS) for CO is 9 parts per million (ppm) in an averaging period of 8 hours and 35 ppm in a 1-hour averaging period.
Accordingly, artificial firelogs that further reduce PM and CO emissions are highly desirable.
Besides generating PM and CO emissions, a burning artificial firelog containing one or more flammable wax binders often produces a disagreeable, waxy odor in the flue smoke and gases. The elimination of such an undesirable odor is another goal of manufacturers of artificial firelogs.
It would also be desirable to increase the length of firelog burn time, and to improve the aesthetic appearance of a burning artificial firelog so that it more nearly resembles a natural wood log during combustion, including the development of white ash as the burn progresses.
In accordance with the broad principles of the present invention, there is provided an artificial firelog comprising combustible cellulosic materials, a combustible binder and an amount of sodium bicarbonate effective to reduce emissions of particulate matter and carbon monoxide during combustion of the firelog. In accordance with a specific, exemplary embodiment of the invention, the sodium bicarbonate comprises about 1% to about 10% by weight of the artificial firelog. Preferably, the sodium bicarbonate comprises about 2% to about 5% by weight of the artificial firelog.
The addition of sodium bicarbonate has been found to provide a substantial reduction in PM and CO emissions during combustion of an artificial firelog, increase the burn time of the firelog, and reduce the xe2x80x9cwaxy malodorxe2x80x9d from the flue smoke and gases. In addition, the xe2x80x9cpoke resistancexe2x80x9d of the firelog, that is, its resistance to collapsing when poked, increases with the amount of sodium bicarbonate ingredient, making the firelog of the invention particularly suitable for outdoor use. Still further, the aesthetic appearance of the burning log is substantially improved, the sodium bicarbonate giving a xe2x80x9chardwoodxe2x80x9d or regular xe2x80x9ccordwoodxe2x80x9d appearance to the log, with charring and a natural appearing white ash developing during the course of combustion.